Pflitsch, C. (Corresponding author)FZJ*

2002
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Report No.: Juel-3951

Abstract: The present PhD-thesis describes the preparation and characterization of thin metal and oxide films (1 - 20 ML) grown an singlecrystalline substrates. The investigations included the preparation of thin iron and iron oxide films an a Cu(110)-substrate as well as the growth of Fe/Fe$_{2}$O$_{3}$ - and Co/Fe$_{2}$O$_{3}$ - double layers. In addition, the oxidation of a CoGa - crystal ((001)-surface) and the growth of thin iron films an that substrate were studied. The films were characterized by thermal energy atom scattering (TEAS), low energy electron diffraction (LEED), and Auger electron spectroscopy (AES). Iron deposited onto a Cu(110)-surface at room temperature leads to the formation of iron islands. At low temperature it is possible to grow an iron film with a well-ordered and smooth surface: A thin iron film (5 ML) grown an Cu(110) at 130 K shows a surface of disordered structure. During annealing up to 240 K the surface becomes ordered, a smooth $\gamma$-Fe(110) film is formed. Annealing the surface to temperatures higher than 240 K leads to the formation of facets. At a temperature of 490 K the iron starts to diffuse into the Cu-bulk. By oxidizing the smooth $\gamma$-Fe(110) film an Cu(110) at a temperature of 130 K a thin Fe203 film is formed. The surface of the oxide becomes ordered during annealing of the film up to 400 K. At temperatures higher than 550 K the oxide starts to be reduced, although Fe$_{2}$O$_{3}$ remains stable at the outermost surface up to 720 K. Above 700 K the oxide film decomposes, and only a very thin FeO film remains an the substrate. This film is stable between 900 and 1100 K. Iron (or Cobalt) deposited at 130 K onto an ordered Fe$_{2}$O$_{3}$ film prepared an Cu(110) leads to the formation of a disordered metal film an the Fe$_{2}$O$_{3}$/Cu(110) substrate. These films become ordered when being annealed: the iron film orders between 400 to 530 K, the cobalt film already at temperatures between 300 to 440 K. In the case of Fe an Fe$_{2}$O$_{3}$ a chemical reaction already takes place between the iron and the iron oxide at temperatures above 350 K. In the case of Co an Fe$_{2}$O$_{3}$ this double layer is stable up to 400 K, which means that no intermixing of Co and Fe$_{2}$O$_{3}$ can be observed below this temperature. Besides the experiments an the Cu(110)-substrate there were also experiments done an a CoGa crystal ((001)-surface): Oxidation of the CoGa(001) at room temperature followed by annealing of the surface up to temperatures higher than 600 K or the oxidation of the surface at high temperatures (600 K < T < 850 K) leads to the formation of a thin $\beta$-Ga$_{2}$O$_{3}$. The order of this oxide film is improved by increasing temperatures of both oxidation and annealing. Above 850 K the $\beta$-Ga$_{2}$O$_{3}$ decomposes and oxygen desorbs. Iron deposited an CoGa(001) between temperatures of 310 and 550 K leads to the formation of well ordered iron films. At 310, 370, and 550 K a layer-by-layer growth mechanism could be observed. The iron film deposited at 550 K is an a-Fe film. For thin films (< 7 ML) an $\alpha$-Fe(001) surface could be observed; thicker films (> 7 ML) show a c(2 x 2)-reconstruction.

Keyword(s): multilayer system ; metallic film ; film deposition ; preparation ; characterization

1. Grenz- und Oberflächen (IBN-3)